Example(taken from chapter 11 in [1]}) Note that if \(\tau =[-1, -\frac{1}{3},\frac{1}{3}, 1]\)  then the differentiation matrix is
\(\mathbf {D}_{\mathrm {Lagrange}}= \left[\begin{array}{cccc}-11 & \phantom{-}18 & -9 & \phantom{-}2\\-2 & -3 & \phantom{-}6 & -1\\\phantom{-}1 & -6 & \phantom{-}3 & \phantom{-}2\\-2 & \phantom{-}9 & -18 & \phantom{-}11\\\end{array}\right],\) 
